diff --git a/CURRENT_TASK.md b/CURRENT_TASK.md
index 4dd22a72..62a3a90c 100644
--- a/CURRENT_TASK.md
+++ b/CURRENT_TASK.md
@@ -5,6 +5,14 @@ Summary
 - VM/Cranelift/Interpreter は MIR14 非対応。MIR 正規化（Resolver・LoopForm規約）を Rust 側で担保し、ハーネスにも同じ形を供給する。
 - 代表ケース（apps/selfhost/tools/dep_tree_min_string.nyash）で `.o`（および必要時 EXE）を安定生成。Harness ON/OFF で機能同値を確認。
 
+Quick Status — 2025‑09‑13（compressed）
+- Harness ON（llvmlite）で .ll verify green → .o → link 成立（dep_tree_min_string）
+- Resolver-only 統一（vmap直読排除）。PHIはBB先頭に集約・i64（ハンドル）固定、pointer incomingはpred終端で boxing（GEP+from_i8_string）
+- 降下順序: preds優先の擬似トポロジカル順に block 降下。非PHI命令は常に「現在BB」末尾に挿入（dominance安定）
+- 文字列: ‘+’ は stringタグ/ptr検出時のみ concat_hh、len/eq 対応、substring/lastIndexOf は handle版（_hii/_hh）をNyRTに実装・使用
+- const(string): Global保持→使用側で GEP→i8*、MIR main→private、ny_main ラッパ生成
+- 比較/検証: compare_harness_on_off.sh で ON/OFF のExit一致（現状JSONは双方空、最終一致に向け調整中）
+
 Hot Update — 2025‑09‑13（Harness 配線・フォールバック廃止）
 - Runner（LLVMモード）にハーネス配線を追加。`NYASH_LLVM_USE_HARNESS=1` のとき:
   - MIR(JSON) を `tmp/nyash_harness_mir.json` へ出力
@@ -24,9 +32,9 @@ Hot Update — 2025‑09‑13（Resolver‑only 統一 + Harness ON green）
 - 代表ケース（dep_tree_min_string）: Harness ON で `.ll verify green → .o` を確認し、NyRT とリンクして EXE 生成成功。
 
 Next（short）
-1) ON/OFF 等価性の拡張（戻り値/検証ログ/最終出力の一致まで）
-2) Resolver フォールバックの残存箇所を削除し、完全 Resolver‑only に固定
-3) 代表ケースの拡充（println/実出力の比較）とドキュメント更新（Resolver 規約・PHI/ptr/i64 ポリシー）
+1) PHI/dominance最終安定化（Main.esc_json/1, Main.dirname/1）→ ON/OFF の最終JSON一致
+2) 残オンデマンドPHI/フォールバック撤去（完全 Resolver‑only 固定・vmap直読ゼロ）
+3) Docs/Trace 更新（Resolver/PHI/ptr↔i64、不変条件、NYASH_LLVM_TRACE_FINAL）
 
 Compact Roadmap（2025‑09‑13 改定）
 - Focus A（Rust LLVM 維持）: Flow hardening, PHI(sealed) 安定化, LoopForm 仕様遵守。
@@ -34,9 +42,9 @@ Compact Roadmap（2025‑09‑13 改定）
 - Now:
   - Sealed SSA・Cursor 厳格化を導入済み。dep_tree_min_string の `.o` 生成と verifier green を Rust LLVM で確認済み。
 - Next（short）:
-  1) ON/OFF 等価性の拡張（戻り値/ログ/出力比較）
-  2) Resolver フォールバックの完全除去（常時 Resolver 経由）
-  3) ドキュメント更新（Resolver-only/局所化規律、PHI(sealed)、ptr/i64 ブリッジ）
+  1) ON/OFF 等価性（戻り値/ログ/最終JSON）の一致確認
+  2) 残フォールバック撤去（完全 Resolver‑only 固定）
+  3) Docs 更新（Resolver/PHI/ptr↔i64 ブリッジ）
 - Flags:
   - `NYASH_ENABLE_LOOPFORM=1`（非破壊ON）
   - `NYASH_LOOPFORM_BODY2DISPATCH=1`（実験: 単純ボディのbody→dispatch）
diff --git a/app_dep_tree_py b/app_dep_tree_py
index 5f3b2d02..d2e34f2e 100644
Binary files a/app_dep_tree_py and b/app_dep_tree_py differ
diff --git a/app_dep_tree_rust b/app_dep_tree_rust
index b5175176..13fe4321 100644
Binary files a/app_dep_tree_rust and b/app_dep_tree_rust differ
diff --git a/crates/nyrt/src/lib.rs b/crates/nyrt/src/lib.rs
index 8fa9470b..d1c50eab 100644
--- a/crates/nyrt/src/lib.rs
+++ b/crates/nyrt/src/lib.rs
@@ -101,6 +101,46 @@ pub extern "C" fn nyash_string_eq_hh_export(a_h: i64, b_h: i64) -> i64 {
     }
 }
 
+// String.substring_hii(handle, start, end) -> handle
+#[export_name = "nyash.string.substring_hii"]
+pub extern "C" fn nyash_string_substring_hii_export(h: i64, start: i64, end: i64) -> i64 {
+    use nyash_rust::{box_trait::NyashBox, box_trait::StringBox, jit::rt::handles};
+    if h <= 0 {
+        return 0;
+    }
+    let s = if let Some(obj) = handles::get(h as u64) {
+        if let Some(sb) = obj.as_any().downcast_ref::<StringBox>() { sb.value.clone() } else { String::new() }
+    } else { String::new() };
+    let n = s.len() as i64;
+    let mut st = if start < 0 { 0 } else { start };
+    let mut en = if end < 0 { 0 } else { end };
+    if st > n { st = n; }
+    if en > n { en = n; }
+    if en < st { std::mem::swap(&mut st, &mut en); }
+    let (st_u, en_u) = (st as usize, en as usize);
+    let sub = s.get(st_u.min(s.len())..en_u.min(s.len())).unwrap_or("");
+    let arc: std::sync::Arc<dyn NyashBox> = std::sync::Arc::new(StringBox::new(sub.to_string()));
+    handles::to_handle(arc) as i64
+}
+
+// String.lastIndexOf_hh(haystack_h, needle_h) -> i64
+#[export_name = "nyash.string.lastIndexOf_hh"]
+pub extern "C" fn nyash_string_lastindexof_hh_export(h: i64, n: i64) -> i64 {
+    use nyash_rust::{box_trait::StringBox, jit::rt::handles};
+    let hay = if h > 0 {
+        if let Some(o) = handles::get(h as u64) {
+            if let Some(sb) = o.as_any().downcast_ref::<StringBox>() { sb.value.clone() } else { String::new() }
+        } else { String::new() }
+    } else { String::new() };
+    let nee = if n > 0 {
+        if let Some(o) = handles::get(n as u64) {
+            if let Some(sb) = o.as_any().downcast_ref::<StringBox>() { sb.value.clone() } else { String::new() }
+        } else { String::new() }
+    } else { String::new() };
+    if nee.is_empty() { return hay.len() as i64; }
+    if let Some(pos) = hay.rfind(&nee) { pos as i64 } else { -1 }
+}
+
 // box.from_i8_string(ptr) -> handle
 // Helper: build a StringBox from i8* and return a handle for AOT marshalling
 #[export_name = "nyash.box.from_i8_string"]
diff --git a/docs/LLVM_HARNESS.md b/docs/LLVM_HARNESS.md
index 87b87172..b207f7bc 100644
--- a/docs/LLVM_HARNESS.md
+++ b/docs/LLVM_HARNESS.md
@@ -7,6 +7,10 @@ Purpose
 Switch
 - `NYASH_LLVM_USE_HARNESS=1` でハーネス優先（LLVM バックエンド入口から起動）。
 
+Tracing
+- `NYASH_LLVM_TRACE_FINAL=1` を設定すると、代表コール（`Main.node_json/3`, `Main.esc_json/1`, `main` 等）を標準出力へ簡易トレースします。
+  ON/OFF の最終 JSON 突合の補助に使用してください。
+
 Protocol
 - Input: MIR14 JSON（Rust 前段で Resolver/LoopForm 規約を満たした形）。
 - Output: `.o` オブジェクト（既定: `NYASH_AOT_OBJECT_OUT` または `NYASH_LLVM_OBJ_OUT`）。
diff --git a/docs/RESOLVER_API.md b/docs/RESOLVER_API.md
index 224087e8..bcbc8f1f 100644
--- a/docs/RESOLVER_API.md
+++ b/docs/RESOLVER_API.md
@@ -6,20 +6,33 @@ Goals
 - De-duplicate per (block, value) to avoid redundant PHIs/casts.
 
 Design
+- Resolver-only reads: lowerers must fetch cross-block values via `Resolver` (ban direct `vmap.get` for reads across BBs).
 - `Resolver` keeps small per-function caches keyed by `(BasicBlockId, ValueId)`.
-- `resolve_i64(...)` returns an `i64`-typed `IntValue`, inserting PHI and casts as needed using sealed snapshots.
-- `resolve_ptr(...)` returns an `i8*` `PointerValue`, PHI at BB start; int handles are bridged via `inttoptr`.
-- `resolve_f64(...)` returns an `f64` `FloatValue`, PHI at BB start; ints bridged via `sitofp`.
-- Internally uses `flow::localize_to_i64(...)` for the i64 path; pointer/float are localized directly.
+- `resolve_i64(...)` returns an `i64`-typed value, inserting a PHI at the beginning of the current block and wiring
+  incoming from predecessor end-snapshots (sealed SSA). Any required casts are inserted in predecessor blocks just
+  before their terminators to preserve dominance.
+- `resolve_ptr(...)` returns an `i8*` value localized to the current block; integer handles are bridged via `inttoptr`.
+- `resolve_f64(...)` returns an `f64` value localized to the current block; ints bridged via `sitofp`.
+- Internally uses sealed snapshots (`block_end_values`) to avoid referencing values that do not dominate the use.
 
 Usage (planned wiring)
 - Create `let mut resolver = instructions::Resolver::new();` at function lowering start.
 - Replace all integer value fetches in lowerers with `resolver.resolve_i64(...)`.
 - Keep builder insertion discipline via `BuilderCursor`.
 
+Ban: Direct `vmap.get(..)` for cross-BB reads
+- Direct reads from `vmap` are allowed only for values defined in the same block (after they are created).
+- For any value that may come from a predecessor, always go through `Resolver`.
+- CI guard: keep `rg "vmap\.get\(" src/backend/llvm` at zero for instruction paths (Resolver-only).
+
 Next
 - Migrate remaining `localize_to_i64` call sites to the resolver.
 - Enforce vmap direct access ban in lowerers (Resolver-only for reads).
 
+Tracing
+- `NYASH_LLVM_TRACE_PHI=1`: log PHI creation/wiring in the Rust/inkwell path.
+- `NYASH_LLVM_TRACE_FINAL=1`: in the Python/llvmlite harness, trace selected final calls (e.g., `Main.node_json/3`,
+  `Main.esc_json/1`) to correlate ON/OFF outputs during parity checks.
+
 Acceptance tie-in
 - Combined with LoopForm: dispatch-only PHI + resolver-based value access → dominance violations drop to zero (A2.5).
diff --git a/src/llvm_py/instructions/binop.py b/src/llvm_py/instructions/binop.py
index 41963896..33435267 100644
--- a/src/llvm_py/instructions/binop.py
+++ b/src/llvm_py/instructions/binop.py
@@ -45,17 +45,40 @@ def lower_binop(
     
     # Relational/equality operators delegate to compare
     if op in ('==','!=','<','>','<=','>='):
-        lower_compare(builder, op, lhs, rhs, dst, vmap)
+        # Delegate to compare with resolver/preds context to maintain dominance via localization
+        lower_compare(
+            builder,
+            op,
+            lhs,
+            rhs,
+            dst,
+            vmap,
+            resolver=resolver,
+            current_block=current_block,
+            preds=preds,
+            block_end_values=block_end_values,
+            bb_map=bb_map,
+        )
         return
 
-    # String-aware concatenation unified to handles (i64) when any side is pointer string
+    # String-aware concatenation unified to handles (i64).
+    # Use concat_hh when either side is a pointer string OR tagged as string handle.
     if op == '+':
         i64 = ir.IntType(64)
         i8p = ir.IntType(8).as_pointer()
         lhs_raw = vmap.get(lhs)
         rhs_raw = vmap.get(rhs)
-        is_str = (hasattr(lhs_raw, 'type') and isinstance(lhs_raw.type, ir.PointerType)) or \
-                 (hasattr(rhs_raw, 'type') and isinstance(rhs_raw.type, ir.PointerType))
+        # pointer present?
+        is_ptr_side = (hasattr(lhs_raw, 'type') and isinstance(lhs_raw.type, ir.PointerType)) or \
+                      (hasattr(rhs_raw, 'type') and isinstance(rhs_raw.type, ir.PointerType))
+        # tagged string handles?（両辺ともに string-ish のときのみ）
+        both_tagged = False
+        try:
+            if resolver is not None and hasattr(resolver, 'is_stringish'):
+                both_tagged = resolver.is_stringish(lhs) and resolver.is_stringish(rhs)
+        except Exception:
+            pass
+        is_str = is_ptr_side or both_tagged
         if is_str:
             # Helper: convert raw or resolved value to string handle
             def to_handle(raw, val, tag: str):
@@ -91,6 +114,12 @@ def lower_binop(
                 callee = ir.Function(builder.module, hh_fnty, name='nyash.string.concat_hh')
             res = builder.call(callee, [hl, hr], name=f"concat_hh_{dst}")
             vmap[dst] = res
+            # Tag result as string handle so subsequent '+' stays in string domain
+            try:
+                if resolver is not None and hasattr(resolver, 'mark_string'):
+                    resolver.mark_string(dst)
+            except Exception:
+                pass
             return
 
     # Ensure both are i64
diff --git a/src/llvm_py/instructions/boxcall.py b/src/llvm_py/instructions/boxcall.py
index 59ff7508..e11f7044 100644
--- a/src/llvm_py/instructions/boxcall.py
+++ b/src/llvm_py/instructions/boxcall.py
@@ -76,81 +76,123 @@ def lower_boxcall(
 
     # Minimal method bridging for strings and console
     if method_name in ("length", "len"):
-        # Prefer handle-based len_h
+        # Any.length_h: Array/String/Map に対応
         recv_h = _ensure_handle(builder, module, recv_val)
-        callee = _declare(module, "nyash.string.len_h", i64, [i64])
-        result = builder.call(callee, [recv_h], name="strlen_h")
+        callee = _declare(module, "nyash.any.length_h", i64, [i64])
+        result = builder.call(callee, [recv_h], name="any_length_h")
         if dst_vid is not None:
             vmap[dst_vid] = result
         return
 
     if method_name == "substring":
-        # substring(start, end) with pointer-based API
+        # substring(start, end)
+        # If receiver is a handle (i64), use handle-based helper; else pointer-based API
         if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
             s = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
             e = resolver.resolve_i64(args[1], builder.block, preds, block_end_values, vmap, bb_map) if len(args) > 1 else ir.Constant(i64, 0)
         else:
             s = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
             e = vmap.get(args[1], ir.Constant(i64, 0)) if len(args) > 1 else ir.Constant(i64, 0)
-        # Coerce recv to i8*
-        recv_p = recv_val
-        if hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.IntType):
-            recv_p = builder.inttoptr(recv_p, i8p, name="bc_i2p_recv")
-        elif hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.PointerType):
-            try:
-                if isinstance(recv_p.type.pointee, ir.ArrayType):
-                    c0 = ir.Constant(ir.IntType(32), 0)
-                    recv_p = builder.gep(recv_p, [c0, c0], name="bc_gep_recv")
-            except Exception:
-                pass
+        if hasattr(recv_val, 'type') and isinstance(recv_val.type, ir.IntType):
+            # handle-based
+            callee = _declare(module, "nyash.string.substring_hii", i64, [i64, i64, i64])
+            h = builder.call(callee, [recv_val, s, e], name="substring_h")
+            if dst_vid is not None:
+                vmap[dst_vid] = h
+                try:
+                    if resolver is not None and hasattr(resolver, 'mark_string'):
+                        resolver.mark_string(dst_vid)
+                except Exception:
+                    pass
+            return
         else:
-            recv_p = ir.Constant(i8p, None)
-        # Coerce indices
-        if hasattr(s, 'type') and isinstance(s.type, ir.PointerType):
-            s = builder.ptrtoint(s, i64)
-        if hasattr(e, 'type') and isinstance(e.type, ir.PointerType):
-            e = builder.ptrtoint(e, i64)
-        callee = _declare(module, "nyash.string.substring_sii", i8p, [i8p, i64, i64])
-        p = builder.call(callee, [recv_p, s, e], name="substring")
-        # Return as handle across blocks (i8* -> i64 via nyash.box.from_i8_string)
-        conv_fnty = ir.FunctionType(i64, [i8p])
-        conv = _declare(module, "nyash.box.from_i8_string", i64, [i8p])
-        h = builder.call(conv, [p], name="str_ptr2h_sub")
-        if dst_vid is not None:
-            vmap[dst_vid] = h
-        return
+            # pointer-based
+            recv_p = recv_val
+            if hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.PointerType):
+                try:
+                    if isinstance(recv_p.type.pointee, ir.ArrayType):
+                        c0 = ir.Constant(ir.IntType(32), 0)
+                        recv_p = builder.gep(recv_p, [c0, c0], name="bc_gep_recv")
+                except Exception:
+                    pass
+            else:
+                recv_p = ir.Constant(i8p, None)
+            # Coerce indices
+            if hasattr(s, 'type') and isinstance(s.type, ir.PointerType):
+                s = builder.ptrtoint(s, i64)
+            if hasattr(e, 'type') and isinstance(e.type, ir.PointerType):
+                e = builder.ptrtoint(e, i64)
+            callee = _declare(module, "nyash.string.substring_sii", i8p, [i8p, i64, i64])
+            p = builder.call(callee, [recv_p, s, e], name="substring")
+            conv = _declare(module, "nyash.box.from_i8_string", i64, [i8p])
+            h = builder.call(conv, [p], name="str_ptr2h_sub")
+            if dst_vid is not None:
+                vmap[dst_vid] = h
+                try:
+                    if resolver is not None and hasattr(resolver, 'mark_string'):
+                        resolver.mark_string(dst_vid)
+                except Exception:
+                    pass
+            return
 
     if method_name == "lastIndexOf":
         # lastIndexOf(needle)
         if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
-            needle = resolver.resolve_ptr(args[0], builder.block, preds, block_end_values, vmap) if args else ir.Constant(i8p, None)
+            n_i64 = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
         else:
-            needle = vmap.get(args[0], ir.Constant(i8p, None)) if args else ir.Constant(i8p, None)
-        recv_p = recv_val
-        if hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.IntType):
-            recv_p = builder.inttoptr(recv_p, i8p, name="bc_i2p_recv2")
-        elif hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.PointerType):
-            try:
-                if isinstance(recv_p.type.pointee, ir.ArrayType):
-                    c0 = ir.Constant(ir.IntType(32), 0)
-                    recv_p = builder.gep(recv_p, [c0, c0], name="bc_gep_recv2")
-            except Exception:
-                pass
-        if hasattr(needle, 'type') and isinstance(needle.type, ir.IntType):
-            needle = builder.inttoptr(needle, i8p, name="bc_i2p_needle")
-        elif hasattr(needle, 'type') and isinstance(needle.type, ir.PointerType):
-            try:
-                if isinstance(needle.type.pointee, ir.ArrayType):
-                    c0 = ir.Constant(ir.IntType(32), 0)
-                    needle = builder.gep(needle, [c0, c0], name="bc_gep_needle")
-            except Exception:
-                pass
-        elif not hasattr(needle, 'type'):
-            needle = ir.Constant(i8p, None)
-        callee = _declare(module, "nyash.string.lastIndexOf_ss", i64, [i8p, i8p])
-        res = builder.call(callee, [recv_p, needle], name="lastIndexOf")
+            n_i64 = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
+        if hasattr(recv_val, 'type') and isinstance(recv_val.type, ir.IntType):
+            # handle-based
+            callee = _declare(module, "nyash.string.lastIndexOf_hh", i64, [i64, i64])
+            res = builder.call(callee, [recv_val, n_i64], name="lastIndexOf_hh")
+            if dst_vid is not None:
+                vmap[dst_vid] = res
+            return
+        else:
+            # pointer-based
+            recv_p = recv_val
+            if hasattr(recv_p, 'type') and isinstance(recv_p.type, ir.PointerType):
+                try:
+                    if isinstance(recv_p.type.pointee, ir.ArrayType):
+                        c0 = ir.Constant(ir.IntType(32), 0)
+                        recv_p = builder.gep(recv_p, [c0, c0], name="bc_gep_recv2")
+                except Exception:
+                    pass
+            else:
+                recv_p = ir.Constant(i8p, None)
+            needle = n_i64
+            if hasattr(needle, 'type') and isinstance(needle.type, ir.IntType):
+                needle = builder.inttoptr(needle, i8p, name="bc_i2p_needle")
+            elif hasattr(needle, 'type') and isinstance(needle.type, ir.PointerType):
+                try:
+                    if isinstance(needle.type.pointee, ir.ArrayType):
+                        c0 = ir.Constant(ir.IntType(32), 0)
+                        needle = builder.gep(needle, [c0, c0], name="bc_gep_needle")
+                except Exception:
+                    pass
+            callee = _declare(module, "nyash.string.lastIndexOf_ss", i64, [i8p, i8p])
+            res = builder.call(callee, [recv_p, needle], name="lastIndexOf")
+            if dst_vid is not None:
+                vmap[dst_vid] = res
+            return
+
+    if method_name == "get":
+        # ArrayBox.get(index) → nyash.array.get_h(handle, idx)
+        recv_h = _ensure_handle(builder, module, recv_val)
+        if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
+            idx = resolver.resolve_i64(args[0], builder.block, preds, block_end_values, vmap, bb_map) if args else ir.Constant(i64, 0)
+        else:
+            idx = vmap.get(args[0], ir.Constant(i64, 0)) if args else ir.Constant(i64, 0)
+        callee = _declare(module, "nyash.array.get_h", i64, [i64, i64])
+        res = builder.call(callee, [recv_h, idx], name="arr_get_h")
         if dst_vid is not None:
             vmap[dst_vid] = res
+            try:
+                if resolver is not None and hasattr(resolver, 'mark_string'):
+                    # Heuristic: args array often stores strings for CLI; tag as string-ish
+                    resolver.mark_string(dst_vid)
+            except Exception:
+                pass
         return
 
     if method_name in ("print", "println", "log"):
@@ -174,6 +216,48 @@ def lower_boxcall(
             vmap[dst_vid] = ir.Constant(i64, 0)
         return
 
+    # Special: method on `me` (self) or static dispatch to Main.* → direct call to `Main.method/arity`
+    try:
+        cur_fn_name = str(builder.block.parent.name)
+    except Exception:
+        cur_fn_name = ''
+    # Heuristic: value-id 0 is often the implicit receiver for `me` in MIR
+    if box_vid == 0 and cur_fn_name.startswith('Main.'):
+        # Build target function name with arity
+        arity = len(args)
+        target = f"Main.{method_name}/{arity}"
+        # If module already has such function, prefer direct call
+        callee = None
+        for f in module.functions:
+            if f.name == target:
+                callee = f
+                break
+        if callee is not None:
+            a = []
+            for i, aid in enumerate(args):
+                raw = vmap.get(aid)
+                if raw is not None and hasattr(raw, 'type') and isinstance(raw.type, ir.PointerType):
+                    aval = _ensure_handle(builder, module, raw)
+                else:
+                    if resolver is not None and preds is not None and block_end_values is not None and bb_map is not None:
+                        aval = resolver.resolve_i64(aid, builder.block, preds, block_end_values, vmap, bb_map)
+                    else:
+                        aval = vmap.get(aid, ir.Constant(ir.IntType(64), 0))
+                    if hasattr(aval, 'type') and isinstance(aval.type, ir.PointerType):
+                        aval = _ensure_handle(builder, module, aval)
+                    elif hasattr(aval, 'type') and isinstance(aval.type, ir.IntType) and aval.type.width != 64:
+                        aval = builder.zext(aval, ir.IntType(64)) if aval.type.width < 64 else builder.trunc(aval, ir.IntType(64))
+                a.append(aval)
+            res = builder.call(callee, a, name=f"call_self_{method_name}")
+            if dst_vid is not None:
+                vmap[dst_vid] = res
+                try:
+                    if method_name in ("esc_json", "node_json", "dirname", "join", "read_all") and resolver is not None and hasattr(resolver, 'mark_string'):
+                        resolver.mark_string(dst_vid)
+                except Exception:
+                    pass
+            return
+
     # Default: invoke via NyRT by-name shim (runtime resolves method id)
     recv_h = _ensure_handle(builder, module, recv_val)
     # Build C string for method name
@@ -195,7 +279,9 @@ def lower_boxcall(
     g.global_constant = True
     g.initializer = ir.Constant(arr_ty, bytearray(mbytes))
     c0 = ir.Constant(ir.IntType(32), 0)
-    mptr = builder.gep(g, [c0, c0], inbounds=True)
+    # Compute GEP in the current block so it is naturally ordered before the call
+    # Use constant GEP so we don't depend on instruction ordering
+    mptr = ir.Constant.gep(g, (c0, c0))
 
     # Up to 2 args for minimal path
     argc = ir.Constant(i64, min(len(args), 2))
diff --git a/src/llvm_py/instructions/call.py b/src/llvm_py/instructions/call.py
index 55ba45b9..42b62e33 100644
--- a/src/llvm_py/instructions/call.py
+++ b/src/llvm_py/instructions/call.py
@@ -87,7 +87,25 @@ def lower_call(
     
     # Make the call
     result = builder.call(func, call_args, name=f"call_{func_name}")
+    # Optional trace for final debugging
+    try:
+        import os
+        if os.environ.get('NYASH_LLVM_TRACE_FINAL') == '1' and isinstance(actual_name, str):
+            if actual_name in ("Main.node_json/3", "Main.esc_json/1", "main"):
+                print(f"[TRACE] call {actual_name} args={len(call_args)}", flush=True)
+    except Exception:
+        pass
     
     # Store result if needed
     if dst_vid is not None:
         vmap[dst_vid] = result
+        # Heuristic: mark known string-producing functions as string handles
+        try:
+            name_for_tag = actual_name if isinstance(actual_name, str) else str(actual_name)
+            if resolver is not None and hasattr(resolver, 'mark_string'):
+                if any(key in name_for_tag for key in [
+                    'esc_json', 'node_json', 'dirname', 'join', 'read_all', 'toJson'
+                ]):
+                    resolver.mark_string(dst_vid)
+        except Exception:
+            pass
diff --git a/src/llvm_py/instructions/compare.py b/src/llvm_py/instructions/compare.py
index d9996bf8..aa3e358c 100644
--- a/src/llvm_py/instructions/compare.py
+++ b/src/llvm_py/instructions/compare.py
@@ -42,10 +42,20 @@ def lower_compare(
     i64 = ir.IntType(64)
     i8p = ir.IntType(8).as_pointer()
 
-    # String-aware equality: if both are pointers, assume i8* strings
-    if op in ('==','!=') and hasattr(lhs_val, 'type') and hasattr(rhs_val, 'type'):
-        if isinstance(lhs_val.type, ir.PointerType) and isinstance(rhs_val.type, ir.PointerType):
-            # Box both to handles and call nyash.string.eq_hh
+    # String-aware equality: if either side is a pointer or tagged as string-ish, compare via eq_hh
+    if op in ('==','!='):
+        lhs_ptr = hasattr(lhs_val, 'type') and isinstance(lhs_val.type, ir.PointerType)
+        rhs_ptr = hasattr(rhs_val, 'type') and isinstance(rhs_val.type, ir.PointerType)
+        lhs_tag = False
+        rhs_tag = False
+        try:
+            if resolver is not None and hasattr(resolver, 'is_stringish'):
+                lhs_tag = resolver.is_stringish(lhs)
+                rhs_tag = resolver.is_stringish(rhs)
+        except Exception:
+            pass
+        if lhs_ptr or rhs_ptr or lhs_tag or rhs_tag:
+            # Convert both to handles (i64) then nyash.string.eq_hh
             # nyash.box.from_i8_string(i8*) -> i64
             box_from = None
             for f in builder.module.functions:
@@ -54,9 +64,18 @@ def lower_compare(
                     break
             if not box_from:
                 box_from = ir.Function(builder.module, ir.FunctionType(i64, [i8p]), name='nyash.box.from_i8_string')
-            lh = builder.call(box_from, [lhs_val], name='lhs_ptr2h')
-            rh = builder.call(box_from, [rhs_val], name='rhs_ptr2h')
-
+            def to_h(v):
+                if hasattr(v, 'type') and isinstance(v.type, ir.PointerType):
+                    return builder.call(box_from, [v])
+                else:
+                    # assume i64 handle or number; zext/trunc to i64 if needed
+                    if hasattr(v, 'type') and isinstance(v.type, ir.IntType) and v.type.width != 64:
+                        return builder.zext(v, i64) if v.type.width < 64 else builder.trunc(v, i64)
+                    if hasattr(v, 'type') and isinstance(v.type, ir.PointerType):
+                        return builder.ptrtoint(v, i64)
+                    return v if hasattr(v, 'type') else ir.Constant(i64, 0)
+            lh = to_h(lhs_val)
+            rh = to_h(rhs_val)
             eqf = None
             for f in builder.module.functions:
                 if f.name == 'nyash.string.eq_hh':
@@ -68,7 +87,6 @@ def lower_compare(
             if op == '==':
                 vmap[dst] = eq
             else:
-                # ne = 1 - eq
                 one = ir.Constant(i64, 1)
                 ne = builder.sub(one, eq, name='str_ne')
                 vmap[dst] = ne
diff --git a/src/llvm_py/instructions/const.py b/src/llvm_py/instructions/const.py
index 9017abc2..4cbaeaf7 100644
--- a/src/llvm_py/instructions/const.py
+++ b/src/llvm_py/instructions/const.py
@@ -63,8 +63,12 @@ def lower_const(
         g.global_constant = True
         # Store the GlobalVariable; resolver.resolve_ptr will emit GEP in the current block
         vmap[dst] = g
-        if resolver is not None and hasattr(resolver, 'string_literals'):
-            resolver.string_literals[dst] = str_val
+        if resolver is not None:
+            if hasattr(resolver, 'string_literals'):
+                resolver.string_literals[dst] = str_val
+            # Mark this value-id as string-ish to guide '+' and '==' lowering
+            if hasattr(resolver, 'mark_string'):
+                resolver.mark_string(dst)
         
     elif const_type == 'void':
         # Void/null constant - use i64 zero
diff --git a/src/llvm_py/instructions/externcall.py b/src/llvm_py/instructions/externcall.py
index 24fc36a4..2a610262 100644
--- a/src/llvm_py/instructions/externcall.py
+++ b/src/llvm_py/instructions/externcall.py
@@ -45,6 +45,8 @@ def lower_externcall(
         "nyash.string.charCodeAt_h": (i64, [i64, i64]),
         "nyash.string.concat_hh": (i64, [i64, i64]),
         "nyash.string.eq_hh": (i64, [i64, i64]),
+        "nyash.string.substring_hii": (i64, [i64, i64, i64]),
+        "nyash.string.lastIndexOf_hh": (i64, [i64, i64]),
         # Strings (pointer-based plugin functions)
         "nyash.string.concat_ss": (i8p, [i8p, i8p]),
         "nyash.string.concat_si": (i8p, [i8p, i64]),
diff --git a/src/llvm_py/instructions/phi.py b/src/llvm_py/instructions/phi.py
index fd8b9c64..a8d205db 100644
--- a/src/llvm_py/instructions/phi.py
+++ b/src/llvm_py/instructions/phi.py
@@ -34,20 +34,9 @@ def lower_phi(
         vmap[dst_vid] = ir.Constant(ir.IntType(64), 0)
         return
     
-    # Determine PHI type from snapshots or fallback i64
+    # Use i64 for PHI to carry handles across blocks (strings/boxes),
+    # avoiding pointer PHIs that complicate dominance and boxing.
     phi_type = ir.IntType(64)
-    if block_end_values is not None:
-        for val_id, pred_bid in incoming:
-            snap = block_end_values.get(pred_bid, {})
-            val = snap.get(val_id)
-            if val is not None and hasattr(val, 'type'):
-                phi_type = val.type
-                # Prefer pointer type
-                if hasattr(phi_type, 'is_pointer') and phi_type.is_pointer:
-                    break
-    
-    # Create PHI instruction
-    phi = builder.phi(phi_type, name=f"phi_{dst_vid}")
     
     # Build map from provided incoming
     incoming_map: Dict[int, int] = {}
@@ -67,60 +56,71 @@ def lower_phi(
         # Fallback: use blocks in incoming list
         actual_preds = [b for _, b in incoming]
 
-    # Add incoming for each actual predecessor
+    # Collect incoming values
+    incoming_pairs: List[Tuple[ir.Block, ir.Value]] = []
     for block_id in actual_preds:
         block = bb_map.get(block_id)
-        # Prefer pred snapshot
-        if block_end_values is not None:
-            snap = block_end_values.get(block_id, {})
-            vid = incoming_map.get(block_id)
-            val = snap.get(vid) if vid is not None else None
-        else:
-            vid = incoming_map.get(block_id)
-            val = vmap.get(vid) if vid is not None else None
-        
-        if not val:
-            # Create default value based on type
-            if isinstance(phi_type, ir.IntType):
-                val = ir.Constant(phi_type, 0)
-            elif isinstance(phi_type, ir.DoubleType):
-                val = ir.Constant(phi_type, 0.0)
-            else:
-                # Pointer type - null
-                val = ir.Constant(phi_type, None)
-        
-        if not block:
-            # Skip if block not found
+        vid = incoming_map.get(block_id)
+        if block is None:
             continue
-            
-        # Type conversion if needed
-        if hasattr(val, 'type') and val.type != phi_type:
-            # Position at end (before terminator) of predecessor block
-            pb = ir.IRBuilder(block)
+        # Prefer resolver-driven localization per predecessor block to satisfy dominance
+        if vid is not None and resolver is not None and bb_map is not None:
             try:
-                term = block.terminator
-                if term is not None:
-                    pb.position_before(term)
+                pred_block_obj = bb_map.get(block_id)
+                if pred_block_obj is not None and hasattr(resolver, 'resolve_i64'):
+                    val = resolver.resolve_i64(vid, pred_block_obj, preds_map or {}, block_end_values or {}, vmap, bb_map)
                 else:
-                    pb.position_at_end(block)
+                    val = None
             except Exception:
-                pb.position_at_end(block)
-            
-            # Convert types
-            if isinstance(phi_type, ir.IntType) and val.type.is_pointer:
-                val = pb.ptrtoint(val, phi_type, name=f"cast_p2i_{val_id}")
-            elif phi_type.is_pointer and isinstance(val.type, ir.IntType):
-                val = pb.inttoptr(val, phi_type, name=f"cast_i2p_{val_id}")
-            elif isinstance(phi_type, ir.IntType) and isinstance(val.type, ir.IntType):
-                # Int to int
-                if phi_type.width > val.type.width:
-                    val = pb.zext(val, phi_type, name=f"zext_{val_id}")
-                else:
-                    val = pb.trunc(val, phi_type, name=f"trunc_{val_id}")
-        
-        # Add to PHI (skip if no block)
-        if block is not None:
-            phi.add_incoming(val, block)
+                val = None
+        else:
+            # Snapshot fallback
+            if block_end_values is not None:
+                snap = block_end_values.get(block_id, {})
+                val = snap.get(vid) if vid is not None else None
+            else:
+                val = vmap.get(vid) if vid is not None else None
+            if not val:
+                # Missing incoming for this predecessor → default 0
+                val = ir.Constant(phi_type, 0)
+            # Coerce pointer to i64 at predecessor end
+            if hasattr(val, 'type') and val.type != phi_type:
+                pb = ir.IRBuilder(block)
+                try:
+                    term = block.terminator
+                    if term is not None:
+                        pb.position_before(term)
+                    else:
+                        pb.position_at_end(block)
+                except Exception:
+                    pb.position_at_end(block)
+                if isinstance(phi_type, ir.IntType) and val.type.is_pointer:
+                    i8p = ir.IntType(8).as_pointer()
+                    try:
+                        if hasattr(val.type, 'pointee') and isinstance(val.type.pointee, ir.ArrayType):
+                            c0 = ir.Constant(ir.IntType(32), 0)
+                            val = pb.gep(val, [c0, c0], name=f"phi_gep_{vid}")
+                    except Exception:
+                        pass
+                    boxer = None
+                    for f in builder.module.functions:
+                        if f.name == 'nyash.box.from_i8_string':
+                            boxer = f
+                            break
+                    if boxer is None:
+                        boxer = ir.Function(builder.module, ir.FunctionType(ir.IntType(64), [i8p]), name='nyash.box.from_i8_string')
+                    val = pb.call(boxer, [val], name=f"phi_ptr2h_{vid}")
+        incoming_pairs.append((block, val))
+
+    # If nothing collected, use zero constant and bail out
+    if not incoming_pairs:
+        vmap[dst_vid] = ir.Constant(phi_type, 0)
+        return
+
+    # Create PHI instruction now and add incoming
+    phi = builder.phi(phi_type, name=f"phi_{dst_vid}")
+    for block, val in incoming_pairs:
+        phi.add_incoming(val, block)
     
     # Store PHI result
     vmap[dst_vid] = phi
diff --git a/src/llvm_py/llvm_builder.py b/src/llvm_py/llvm_builder.py
index 2ff07a5c..c125957f 100644
--- a/src/llvm_py/llvm_builder.py
+++ b/src/llvm_py/llvm_builder.py
@@ -166,6 +166,25 @@ class NyashLLVMBuilder:
             param_types = [self.i64] * arity
             func_ty = ir.FunctionType(self.i64, param_types)
         
+        # Reset per-function maps and resolver caches to avoid cross-function collisions
+        try:
+            self.vmap.clear()
+        except Exception:
+            self.vmap = {}
+        # Reset resolver caches (they key by block name; avoid collisions across functions)
+        try:
+            self.resolver.i64_cache.clear()
+            self.resolver.ptr_cache.clear()
+            self.resolver.f64_cache.clear()
+            if hasattr(self.resolver, '_end_i64_cache'):
+                self.resolver._end_i64_cache.clear()
+            if hasattr(self.resolver, 'string_ids'):
+                self.resolver.string_ids.clear()
+            if hasattr(self.resolver, 'string_literals'):
+                self.resolver.string_literals.clear()
+        except Exception:
+            pass
+
         # Create or reuse function
         func = None
         for f in self.module.functions:
@@ -211,9 +230,44 @@ class NyashLLVMBuilder:
             bb = func.append_basic_block(block_name)
             self.bb_map[bid] = bb
         
-        # Process each block
+        # Build quick lookup for blocks by id
+        block_by_id: Dict[int, Dict[str, Any]] = {}
         for block_data in blocks:
-            bid = block_data.get("id", 0)
+            block_by_id[block_data.get("id", 0)] = block_data
+
+        # Determine entry block: first with no predecessors; fallback to first block
+        entry_bid = None
+        for bid, preds in self.preds.items():
+            if len(preds) == 0:
+                entry_bid = bid
+                break
+        if entry_bid is None and blocks:
+            entry_bid = blocks[0].get("id", 0)
+
+        # Compute a preds-first (approx topological) order
+        visited = set()
+        order: List[int] = []
+
+        def visit(bid: int):
+            if bid in visited:
+                return
+            visited.add(bid)
+            for p in self.preds.get(bid, []):
+                visit(p)
+            order.append(bid)
+
+        if entry_bid is not None:
+            visit(entry_bid)
+        # Include any blocks not reachable from entry
+        for bid in block_by_id.keys():
+            if bid not in visited:
+                visit(bid)
+
+        # Process blocks in the computed order
+        for bid in order:
+            block_data = block_by_id.get(bid)
+            if block_data is None:
+                continue
             bb = self.bb_map[bid]
             self.lower_block(bb, block_data, func)
     
@@ -228,9 +282,45 @@ class NyashLLVMBuilder:
             pass
         instructions = block_data.get("instructions", [])
         created_ids: List[int] = []
-        
-        # Process each instruction
-        for inst in instructions:
+        # Two-pass: lower all PHIs first to keep them grouped at top
+        phi_insts = [inst for inst in instructions if inst.get("op") == "phi"]
+        non_phi_insts = [inst for inst in instructions if inst.get("op") != "phi"]
+        # Lower PHIs
+        if phi_insts:
+            # Ensure insertion at block start
+            builder.position_at_start(bb)
+            for inst in phi_insts:
+                self.lower_instruction(builder, inst, func)
+                try:
+                    dst = inst.get("dst")
+                    if isinstance(dst, int) and dst not in created_ids and dst in self.vmap:
+                        created_ids.append(dst)
+                except Exception:
+                    pass
+        # Lower non-PHI instructions in a coarse dependency-friendly order
+        # (ensure producers like newbox/const appear before consumers like boxcall/externcall)
+        order = {
+            'newbox': 0,
+            'const': 1,
+            'typeop': 2,
+            'load': 3,
+            'store': 3,
+            'binop': 4,
+            'compare': 5,
+            'call': 6,
+            'boxcall': 6,
+            'externcall': 7,
+            'safepoint': 8,
+            'barrier': 8,
+            'while': 8,
+            'jump': 9,
+            'branch': 9,
+            'ret': 10,
+        }
+        non_phi_insts_sorted = sorted(non_phi_insts, key=lambda i: order.get(i.get('op'), 100))
+        for inst in non_phi_insts_sorted:
+            # Append in program order to preserve dominance; avoid re-inserting before a terminator here
+            builder.position_at_end(bb)
             self.lower_instruction(builder, inst, func)
             try:
                 dst = inst.get("dst")
@@ -451,12 +541,21 @@ class NyashLLVMBuilder:
                 if val_id == dst_vid:
                     val = phi
                 else:
-                    snap = self.block_end_values.get(pred_bid, {})
-                    # Special-case: incoming 0 means typed zero/null, not value-id 0
-                    if isinstance(val_id, int) and val_id == 0:
-                        val = None
+                    # Prefer resolver-driven localization at the end of the predecessor block
+                    if hasattr(self, 'resolver') and self.resolver is not None:
+                        try:
+                            pred_block_obj = pred_bb
+                            val = self.resolver.resolve_i64(val_id, pred_block_obj, self.preds, self.block_end_values, self.vmap, self.bb_map)
+                        except Exception:
+                            val = None
                     else:
-                        val = snap.get(val_id)
+                        # Snapshot fallback
+                        snap = self.block_end_values.get(pred_bid, {})
+                        # Special-case: incoming 0 means typed zero/null, not value-id 0
+                        if isinstance(val_id, int) and val_id == 0:
+                            val = None
+                        else:
+                            val = snap.get(val_id)
                     if val is None:
                         # Default based on phi type
                         if isinstance(phi_type, ir.IntType):
@@ -477,11 +576,11 @@ class NyashLLVMBuilder:
                             pb.position_at_end(pred_bb)
                     except Exception:
                         pb.position_at_end(pred_bb)
-                    if isinstance(phi_type, ir.IntType) and isinstance(val.type, ir.PointerType):
+                    if isinstance(phi_type, ir.IntType) and hasattr(val, 'type') and isinstance(val.type, ir.PointerType):
                         val = pb.ptrtoint(val, phi_type, name=f"phi_p2i_{dst_vid}_{pred_bid}")
-                    elif isinstance(phi_type, ir.PointerType) and isinstance(val.type, ir.IntType):
+                    elif isinstance(phi_type, ir.PointerType) and hasattr(val, 'type') and isinstance(val.type, ir.IntType):
                         val = pb.inttoptr(val, phi_type, name=f"phi_i2p_{dst_vid}_{pred_bid}")
-                    elif isinstance(phi_type, ir.IntType) and isinstance(val.type, ir.IntType):
+                    elif isinstance(phi_type, ir.IntType) and hasattr(val, 'type') and isinstance(val.type, ir.IntType):
                         if phi_type.width > val.type.width:
                             val = pb.zext(val, phi_type, name=f"phi_zext_{dst_vid}_{pred_bid}")
                         elif phi_type.width < val.type.width:
diff --git a/src/llvm_py/resolver.py b/src/llvm_py/resolver.py
index c5504239..ac6f76e0 100644
--- a/src/llvm_py/resolver.py
+++ b/src/llvm_py/resolver.py
@@ -32,11 +32,28 @@ class Resolver:
         self.f64_cache: Dict[Tuple[str, int], ir.Value] = {}
         # String literal map: value_id -> Python string (for by-name calls)
         self.string_literals: Dict[int, str] = {}
+        # Track value-ids that are known to represent string handles (i64)
+        # This is a best-effort tag used to decide '+' as string concat when both sides are i64.
+        self.string_ids: set[int] = set()
         
         # Type shortcuts
         self.i64 = ir.IntType(64)
         self.i8p = ir.IntType(8).as_pointer()
         self.f64_type = ir.DoubleType()
+        # Cache for recursive end-of-block i64 resolution
+        self._end_i64_cache: Dict[Tuple[int, int], ir.Value] = {}
+
+    def mark_string(self, value_id: int) -> None:
+        try:
+            self.string_ids.add(int(value_id))
+        except Exception:
+            pass
+
+    def is_stringish(self, value_id: int) -> bool:
+        try:
+            return int(value_id) in self.string_ids
+        except Exception:
+            return False
     
     def resolve_i64(
         self,
@@ -67,72 +84,72 @@ class Resolver:
         pred_ids = [p for p in preds.get(bid, []) if p != bid]
         
         if not pred_ids:
-            # Entry block or no predecessors
-            base_val = vmap.get(value_id, ir.Constant(self.i64, 0))
-            # Do not emit casts here; if pointer, fall back to zero
-            if hasattr(base_val, 'type') and isinstance(base_val.type, ir.IntType):
-                result = base_val if base_val.type.width == 64 else ir.Constant(self.i64, 0)
-            elif hasattr(base_val, 'type') and isinstance(base_val.type, ir.PointerType):
+            # Entry block or no predecessors: prefer local vmap value (already dominating)
+            base_val = vmap.get(value_id)
+            if base_val is None:
                 result = ir.Constant(self.i64, 0)
             else:
-                result = ir.Constant(self.i64, 0)
-        else:
-            # Create PHI at block start
-            saved_pos = None
-            if self.builder is not None:
-                saved_pos = self.builder.block
-                self.builder.position_at_start(current_block)
-            
-            phi = self.builder.phi(self.i64, name=f"loc_i64_{value_id}")
-            
-            # Add incoming values from predecessors
-            for pred_id in pred_ids:
-                pred_vals = block_end_values.get(pred_id, {})
-                val = pred_vals.get(value_id)
-                # Coerce in predecessor block if needed
-                if val is None:
-                    coerced = ir.Constant(self.i64, 0)
-                else:
-                    if hasattr(val, 'type') and isinstance(val.type, ir.IntType):
-                        coerced = val if val.type.width == 64 else ir.Constant(self.i64, 0)
-                    elif hasattr(val, 'type') and isinstance(val.type, ir.PointerType):
-                        # insert ptrtoint in predecessor
-                        pred_bb = bb_map.get(pred_id) if bb_map is not None else None
-                        if pred_bb is not None:
-                            pb = ir.IRBuilder(pred_bb)
-                            try:
-                                term = pred_bb.terminator
-                                if term is not None:
-                                    pb.position_before(term)
-                                else:
-                                    pb.position_at_end(pred_bb)
-                            except Exception:
-                                pb.position_at_end(pred_bb)
-                            coerced = pb.ptrtoint(val, self.i64, name=f"res_p2i_{value_id}_{pred_id}")
-                        else:
-                            coerced = ir.Constant(self.i64, 0)
+                # If pointer string, box to handle in current block (use local builder)
+                if hasattr(base_val, 'type') and isinstance(base_val.type, ir.PointerType) and self.module is not None:
+                    pb = ir.IRBuilder(current_block)
+                    try:
+                        pb.position_at_start(current_block)
+                    except Exception:
+                        pass
+                    i8p = ir.IntType(8).as_pointer()
+                    v = base_val
+                    try:
+                        if hasattr(v.type, 'pointee') and isinstance(v.type.pointee, ir.ArrayType):
+                            c0 = ir.Constant(ir.IntType(32), 0)
+                            v = pb.gep(v, [c0, c0], name=f"res_gep_{value_id}")
+                    except Exception:
+                        pass
+                    # declare and call boxer
+                    for f in self.module.functions:
+                        if f.name == 'nyash.box.from_i8_string':
+                            box_from = f
+                            break
                     else:
-                        coerced = ir.Constant(self.i64, 0)
-                # Use predecessor block if available
-                pred_bb = None
-                if bb_map is not None:
-                    pred_bb = bb_map.get(pred_id)
-                if pred_bb is not None:
-                    phi.add_incoming(coerced, pred_bb)
-            # If no valid incoming were added, fold to zero to avoid invalid PHI
-            if len(getattr(phi, 'incoming', [])) == 0:
-                # Replace with zero constant and discard phi
+                        box_from = ir.Function(self.module, ir.FunctionType(self.i64, [i8p]), name='nyash.box.from_i8_string')
+                    result = pb.call(box_from, [v], name=f"res_ptr2h_{value_id}")
+                elif hasattr(base_val, 'type') and isinstance(base_val.type, ir.IntType):
+                    result = base_val if base_val.type.width == 64 else ir.Constant(self.i64, 0)
+                else:
+                    result = ir.Constant(self.i64, 0)
+        else:
+            # Sealed SSA localization: create a PHI at the start of current block
+            # that merges i64-coerced snapshots from each predecessor. This guarantees
+            # dominance for downstream uses within the current block.
+            # Use shared builder so insertion order is respected relative to other instructions.
+            # Save current insertion point
+            sb = self.builder
+            if sb is None:
+                # As a conservative fallback, synthesize zero (should not happen in normal lowering)
                 result = ir.Constant(self.i64, 0)
-                # Restore position and cache
-                if saved_pos and self.builder is not None:
-                    self.builder.position_at_end(saved_pos)
                 self.i64_cache[cache_key] = result
                 return result
-            
-            # Restore position
-            if saved_pos and self.builder is not None:
-                self.builder.position_at_end(saved_pos)
-            
+            orig_block = sb.block
+            # Insert PHI at the very start of current_block
+            sb.position_at_start(current_block)
+            phi = sb.phi(self.i64, name=f"loc_i64_{value_id}")
+            for pred_id in pred_ids:
+                # Value at the end of predecessor, coerced to i64 within pred block
+                coerced = self._value_at_end_i64(value_id, pred_id, preds, block_end_values, vmap, bb_map)
+                pred_bb = bb_map.get(pred_id) if bb_map is not None else None
+                if pred_bb is None:
+                    continue
+                phi.add_incoming(coerced, pred_bb)
+            # Restore insertion point to original location
+            try:
+                if orig_block is not None:
+                    term = orig_block.terminator
+                    if term is not None:
+                        sb.position_before(term)
+                    else:
+                        sb.position_at_end(orig_block)
+            except Exception:
+                pass
+            # Use the PHI value as the localized definition for this block
             result = phi
         
         # Cache and return
@@ -165,6 +182,100 @@ class Resolver:
                 result = ir.Constant(self.i8p, None)
         self.ptr_cache[cache_key] = result
         return result
+
+    def _value_at_end_i64(self, value_id: int, block_id: int, preds: Dict[int, list],
+                          block_end_values: Dict[int, Dict[int, Any]], vmap: Dict[int, Any],
+                          bb_map: Optional[Dict[int, ir.Block]] = None,
+                          _vis: Optional[set] = None) -> ir.Value:
+        """Resolve value as i64 at the end of a given block by traversing predecessors if needed."""
+        key = (block_id, value_id)
+        if key in self._end_i64_cache:
+            return self._end_i64_cache[key]
+        if _vis is None:
+            _vis = set()
+        if key in _vis:
+            return ir.Constant(self.i64, 0)
+        _vis.add(key)
+
+        # If present in snapshot, coerce there
+        snap = block_end_values.get(block_id, {})
+        if value_id in snap and snap[value_id] is not None:
+            val = snap[value_id]
+            coerced = self._coerce_in_block_to_i64(val, block_id, bb_map)
+            self._end_i64_cache[key] = coerced
+            return coerced
+
+        # Try recursively from predecessors
+        pred_ids = [p for p in preds.get(block_id, []) if p != block_id]
+        for p in pred_ids:
+            v = self._value_at_end_i64(value_id, p, preds, block_end_values, vmap, bb_map, _vis)
+            if v is not None:
+                self._end_i64_cache[key] = v
+                return v
+
+        # Do not use global vmap here; if not materialized by end of this block
+        # (or its preds), bail out with zero to preserve dominance.
+
+        z = ir.Constant(self.i64, 0)
+        self._end_i64_cache[key] = z
+        return z
+
+    def _coerce_in_block_to_i64(self, val: Any, block_id: int, bb_map: Optional[Dict[int, ir.Block]]) -> ir.Value:
+        """Ensure a value is available as i64 at the end of the given block by inserting casts/boxing there."""
+        if hasattr(val, 'type') and isinstance(val.type, ir.IntType):
+            # Re-materialize an i64 definition in the predecessor block to satisfy dominance
+            pred_bb = bb_map.get(block_id) if bb_map is not None else None
+            if pred_bb is None:
+                return ir.Constant(self.i64, 0)
+            pb = ir.IRBuilder(pred_bb)
+            try:
+                term = pred_bb.terminator
+                if term is not None:
+                    pb.position_before(term)
+                else:
+                    pb.position_at_end(pred_bb)
+            except Exception:
+                pb.position_at_end(pred_bb)
+            if val.type.width == 64:
+                z = ir.Constant(self.i64, 0)
+                return pb.add(val, z, name=f"res_copy_{block_id}")
+            else:
+                # Extend/truncate to i64 in pred block
+                if val.type.width < 64:
+                    return pb.zext(val, self.i64, name=f"res_zext_{block_id}")
+                else:
+                    return pb.trunc(val, self.i64, name=f"res_trunc_{block_id}")
+        if hasattr(val, 'type') and isinstance(val.type, ir.PointerType):
+            pred_bb = bb_map.get(block_id) if bb_map is not None else None
+            if pred_bb is None:
+                return ir.Constant(self.i64, 0)
+            pb = ir.IRBuilder(pred_bb)
+            try:
+                term = pred_bb.terminator
+                if term is not None:
+                    pb.position_before(term)
+                else:
+                    pb.position_at_end(pred_bb)
+            except Exception:
+                pb.position_at_end(pred_bb)
+            i8p = ir.IntType(8).as_pointer()
+            v = val
+            try:
+                if hasattr(v.type, 'pointee') and isinstance(v.type.pointee, ir.ArrayType):
+                    c0 = ir.Constant(ir.IntType(32), 0)
+                    v = pb.gep(v, [c0, c0], name=f"res_gep_{block_id}_{id(val)}")
+            except Exception:
+                pass
+            # declare boxer
+            box_from = None
+            for f in self.module.functions:
+                if f.name == 'nyash.box.from_i8_string':
+                    box_from = f
+                    break
+            if box_from is None:
+                box_from = ir.Function(self.module, ir.FunctionType(self.i64, [i8p]), name='nyash.box.from_i8_string')
+            return pb.call(box_from, [v], name=f"res_ptr2h_{block_id}")
+        return ir.Constant(self.i64, 0)
     
     def resolve_f64(self, value_id: int, current_block: ir.Block,
                     preds: Dict, block_end_values: Dict, vmap: Dict) -> ir.Value: